The precision with which people make decisions can be predicted by measuring pupil size, according to a study in the journal PLOS Computational Biology.

The research, conducted by Peter Murphy and colleagues at Leiden University in The Netherlands, shows spontaneous, moment-to-moment fluctuations in pupil size predict how people good people are at decision making.

A larger pupil size indicates poorer upcoming task performance, due to more variability in the decisions made once they have the relevant information.

The authors also found that certain individuals who had the largest pupils overall also tended to be the least consistent in their decisions.

The findings open up areas for future research aimed at improving the precision with which we make decisions.

Murphy says we are constantly required to make decisions about the world we live in.

“Researchers have long known that the accuracy and reliability of such everyday decision making can be tremendously variable for different people at different times, but we understand quite little about where this variability comes from,” he says.